This invention in general relates to optical fabrication techniques and in particular to a method by which an optical layer with a predetermined surface contour can be accurately formed on a glass optical element to change the optical performance characteristics of the glass element in a desired way.
As is well known, the design of optical systems is to a great extent influenced by the methods available for accurately and economically fabricating their components or elements. Consequently, designers favor spherical surfaces whenever possible because they can be economically generated with great accuracy by the well-known method of random grinding and polishing.
Conversely, nonspherical or aspheric surfaces are generally avoided, except when no other solution is possible, because the simple principle of random grinding and polishing which generates a sphere must necessarily be replaced by more elaborate and expensive means. However, aspherics can be made in modest production quantities if high precision is not required. A cam guided diamond grinding wheel usually is employed to generate the surface as precisely as possible. Then the surface is fine ground and polished with flexible tools taking care not to destroy the basic shape. If high precision is requied, hand correction is practically a necessity.
Aspherics can also be molded of suitable optical plastics and are very practical made in this manner but can only be used whenever the quantities required are sufficient enough to justify the cost of the required molds.
Consequently, there is a need for a method by which aspheric surfaces can be accurately and economically fabricated, particularly in situations where the volume requirements are low as, for example, in the fabrication of large optics or prototype systems.
Therefore, it is a primary object of the present invention to provide a convenient method by which aspheric surfaces can be generated.
It is another object of the present invention to provide a method by which an optical layer with an aspheric surface can be formed over a glass element to change the optical performance characteristics of the glass element.
It is still another object of the present invention to provide a method by which an optical layer can be formed over a glass element to simulate the optical action of an aspheric element fabricated of material different from either the glass or the layer.
Other objects of the invention will, in part, be obvious and will, in part, appear hereinafter. The invention accordingly comprises the steps of a method and apparatus which are exemplified in the following detailed description and products made with the method.